This invention relates generally to heat exchangers for air conditioning systems and, more particularly, to a method and apparatus for leak testing of heat exchangers to be charged with refrigerant.
There are many different ways of testing the integrity of a coil or heat exchanger used in residential, commercial or industrial air conditioning and heating systems, but all of them require the use of a trace gas and a surrounding matrix against which escape of the trace gas is detectable either visibly or by the use of instruments. Such trace gases, ranging from refrigerants to inert gases, are used either to pressurize the component prior to leak detection of the outer geometry of the part or forming a surrounding environment on the component itself while the latter is subject to internal vacuum.
The cost of the testing process is dictated not only on the original equipment initial costs, but on the cost of use of the trace gas in itself. The very nature of this approach imposes a potential impact on the factory environment due to the escape of gas and non-contained leakage points.
Trace gas escapes to the factory environment are greatly undesirable not only because they represent waste in terms of cost (non recyclable nor reusable gas emissions), but also because of the increasing environmental codes and regulation in all the major HVAC regions of the world including North, Central and South America, and particularly in Asia and Europe.
Another variation of the trace gas systems is the so called “Air under Water” process, very common in today's HVAC industry because of its relative simplicity. This process uses the principle of pressurizing the heat exchanger or coil with air to a specific design pressure, capping the heat exchanger so that it will maintain the pressure, and then submerging the component in clear water to detect leaking hole size and location by visual inspection of the air bubbles. This process has the disadvantage of also producing water emissions. As of now, there are very few testing systems that are “clean” and emission free.
Thermal imaging systems work on the principle that all bodies have a given amount of radiation of heat depending on their actual surface temperature, surrounding energy sources (i.e. light, heat, etc . . . ), surface conditions and physical properties of the material that they are made of. A special infra-red camera device adjusted to work on the infra-red light spectrum frequency range is able to detect the different temperature gradient areas or zones on the body surface. This video image is then fed to a computer for imaging processing, so that it can graphically display the temperature distribution on a screen for analysis and interpretation. Thermal imaging systems are commercially available with different detection sensitivities for use in diverse ways in the medical and industrial fields, such as insulated steam pipe leak/breakage point location for maintenance work, main water underground pipe leaks, medical body scans, etc . . .
It is therefore an object of the present invention to provide an improved method and apparatus for leak testing of heat exchanger coils.
Another object of the present invention is the provision for a leak testing method which reduces the occurrence of introducing trace gases to the environment.
Yet another object of the present invention is the provision for reducing the waste that results from loss of trace gases during leak testing.
Still another object of the present invention is the provision for a heat exchanger leak testing process that is efficient and effective in use.
These objects and other features and advantages become more readily apparent upon reference to the following description when taken in conjunction with the appended drawings.